Active carbon is contemplated herein for use both in its unmodified form and as catalyzed or activated with various procedures for deposition of catalytic materials therein or thereon, e.g., noble metals such as silver, platinum, palladium, spinels, e.g., mixed metal oxides of nickel and cobalt, such as NiCO.sub.2 O.sub.4 ; perovskites, e.g., CaTiO.sub.3, etc. as described at pages 54-44 et seq. of ADVANCED INORGANIC CHEMISTRY by F. Albert Cotton and Geoffrey Wilkinson, Third Edition, INTERSCIENCE PUBLISHERS.
The longevity in actual use of the enhanced active carbon particles in the corrosive environment of a chlor-alkali cell has left much to be desired. Depending upon the particular type(s) of carbon used, and frequently the impurities and content thereof, the length of actual service use in a chlor-alkali cell has been irregular and difficult to reproduce.
In accordance with this invention, it has been learned that by separately contacting the active carbon particles with an alkali (at elevated temperatures) and an acid the porosity of the active carbon is increased and accompanied by greater stability of the active carbon-containing catalyst layer(s) when the active carbon is formulated with other components and prepared either in rolled sheet form or in the form of a sintered flat electrode and incorporated into an electrochemical cell for production of chlorine and caustic.